The use of introducers for the performance of endoluminal medical treatments has become widespread as a result of the clinical and medical advantages over open surgical procedures. The use of introducers does, however, present difficulties, particularly with regard to accurate and reliable placement of the distal end of the introducer within the vasculature or other organs of the patient. While use of imaging methods such as fluoroscopy and X-ray or CRT imaging can enable the clinician to view the embedded distal end of the introducer in the patient, these imaging methods are not optimal. Ultrasonic imaging is a much more preferable imaging technique. However, introducer assemblies, particularly sheaths, catheters and the like, tend not to be readily visible by this technique. While it is possible to build into the introducer elements which are, for instance, radiopaque, this can typically affect the structure and performance of the device and is thus not always practical.
Various designs of introducer assemblies are disclosed, for example, in U.S. Pat. No. 4,425,682, U.S. Pat. No. 5,074,870, U.S. Pat. No. 5,873,813, U.S. Pat. No. 5,979,020, U.S. Pat. No. 6,497,010.